Note 8 - Goodwill and Intangible Assets - Balances of Acquired Intangible Assets, Excluding Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Original cost	$ 218.5	$ 203.0
Accumulated amortization	(92.3)	(65.3)
Intangible Assets, Net	126.2	137.7
Customer Lists [Member]
Original cost	166.2	154.1
Accumulated amortization	(70.3)	(49.8)
Intangible Assets, Net	$ 95.9	$ 104.3
Weighted-average original life (in years) (Year)	15 years	15 years
Trade Names [Member]
Original cost	$ 34.4	$ 31.8
Accumulated amortization	(12.3)	(8.2)
Intangible Assets, Net	$ 22.1	$ 23.6
Weighted-average original life (in years) (Year)	11 years	11 years
Technology-Based Intangible Assets [Member]
Original cost	$ 17.9	$ 17.1
Accumulated amortization	(9.7)	(7.3)
Intangible Assets, Net	$ 8.2	$ 9.8
Weighted-average original life (in years) (Year)	11 years	11 years